RU2114202C1 - Method of producing noble metals from carbonaceous materials - Google Patents

Abstract

FIELD: chemical industry, more particularly recovery of noble metals from waste products, catalysts and other materials on carbonaceous carrier. SUBSTANCE: carbonaceous material is treated using alkali metal carbonates. Initial material in amount of 2.6-6.0 % by weight of carbonates is charged onto surface of carbonate melt and maintained at 930-1100 C till complete oxidation of carbon. Prior to charging initial material, metal collector is added to carbonate melt. The carbonate melt includes mixture of sodium and potassium carbonates in 1:(0.3-1) ratio, and metal collector includes lead. More efficient treatment of carbonaceous material containing noble metals and greater recovery of crude lead comprising up to 50% gold and silver. EFFECT: more efficient production method. 3 cl, 2 dwg

Description

 The invention relates to non-ferrous metallurgy, in particular to methods for extracting precious metals from waste, catalysts and concentrates on a carbon carrier.

 Known methods for processing wastes containing precious metals, hydrochemical methods, which use acids, chlorine, bromides, cyanides and other toxic compounds [1]. The methods make it possible to recover precious metals from various wastes, but additional processing and neutralization of toxic solvents is required. It is especially difficult to extract silver and gold from coal sorbents and catalysts, since they are very porous and liquid solvents do not penetrate into the pores in which noble metals are deposited.

 Known methods for processing gold-containing waste by crucible melting, melting in reflective furnaces and in shaft furnaces [1].

 When melting in crucible furnaces, fine-grained materials are loaded under a layer of larger waste and other materials to reduce dust removal. The smelting of coal materials containing noble metals is almost inevitably accompanied by a large dust removal and loss of noble metals.

 From publicly available patent information, methods for processing materials and wastes containing precious metals are known.

 A known method of processing battery scrap, including crushing, separation by specific gravity in a solution of caustic soda and sodium carbonate, together with hydroxide and lead carbonate, along which silver is extracted along with screw [2].

 However, the known method does not provide a sufficiently complete extraction of silver and, in addition, cannot be used for any types of carbon wastes containing noble metals.

 In technical essence, closer to the proposed invention is a method of processing a mixture containing silver [3]. The method relates to the metallurgy of precious metals and includes the extraction of silver from waste, such as photozol. Material containing silver is mixed with a mixture of reagents, consisting of 25-30% borax and 75-50% sodium carbonate, and melted.

 However, according to the known method, it is possible to process only oxidized materials, for other types of waste containing noble metals, it is necessary to carry out two pyrometallurgical stages. Using a mixture of soda and borax is one-time. When melting, inevitably the release of sublimates containing silver, in which part of the silver is lost with slag, i.e. they must be disposed of.

 The problem to which the invention was directed, is to provide the possibility of processing carbon materials and waste containing noble metals with high efficiency by extracting them to obtain verkbley.

The problem is achieved in that in the method of processing a material containing noble metals using alkali metal carbonates according to the invention, the starting material in the amount of 2.6 - 6.0% by weight of carbonates is loaded onto the surface of the carbonate melt and kept at 930 - 1100 ^o C until the carbon is completely oxidized, while a metal collector is introduced into the carbonate melt before loading the starting material. A mixture of sodium and potassium carbonates in a ratio of 1: 0.3 - 1 is taken as a melt of carbonates, and lead is used as a collector metal.

In a resistance furnace or crucible furnace, a layer of carbonates (Na ₂ CO ₃ or a mixture of Na ₂ CO ₃ - K ₂ CO ₃ ) is deposited, into which the metal-collector is loaded and melted with a layer sufficient to cover the bottom of the unit, carbon material is loaded onto the surface of the molten salt containing gold or silver, or mixtures thereof (or platinoids), and carbon is oxidized, and the resulting small drops of precious metals are lowered to the bottom of the unit and accumulated in the collector. Melt of carbonates is a medium for the oxidation of carbon. The loading of the starting carbonaceous material onto the surface of the carbonate melt ensures complete carbon combustion and the release of noble metals by releasing and passing them through the melt layer. This is achieved by reducing the mass of the melt and the formation of CO, volatile metal oxides, so carbon moistened with a carbonate melt burns, and the interaction of the starting material with carbonates allows it to be burned without being carried into the atmosphere.

 The loading of the collector metal, in this case lead, is necessary to cover the bottom of the smelting unit and depends on the dimensions of the furnace and the time of its operation between castings of the alloy. With continuous operation of the furnace and periodic casting of the alloy, its height should be several times higher than the dimensions of the notch in order not to release molten salts with the alloy. In a crucible furnace, the amount of lead is not important, since when receiving an alloy with 50-60% of the noble metals, both the alloy and salts are poured out at once and separated after solidification. Salts can be used in remelting.

 The process is carried out until the accumulation of noble metals of 50-60% in the collector, then the alloy is removed, a new portion of the collector metal is loaded and the noble metals are deposited again.

The amount of feed source material is 1 to 2.4 g / cm ^{2 of the} surface of the melt (preferably 1.2 to 1.8 g / cm ³ ), which is the mass of a simultaneously loaded portion of 2.6 to 6.0% by weight of the melt. The amount of feed starting material relative to the mass of the carbonate melt allows the process to be carried out without loss of precious metals. An increase in the portion of the loaded carbon-containing material by more than 6.0% increases its rate of interaction with the molten carbonates, there is a sharp intensification of the oxidation process and dust particles of metals can be entrained. Reducing the amount of material loaded does not increase recovery rates, but increases cycle times.

 In FIG. 1 and 2 are graphs confirming the relationship of temperature, the amount of feed material in the melt and the rationale for the claimed parameters.

For optimal results, it is necessary to maintain the temperature in the range of 930 - 1100 ^o C.

A lower temperature leads to a decrease in productivity due to a slower interaction of coal with carbonate, as well as oxidation of carbon by air, a temperature of more than 1100 ^o C leads to the decomposition of carbonates and their strong evaporation. The claimed concentration of sodium and potassium carbonates in the temperature range of the process 930 - 1100 ^o C ensures their molten state and is optimal, therefore, an increase or decrease in the concentration of one of the components can lead to freezing of the melt and disruption of the process.

 The method was carried out as follows.

Example 1. In a shaft resistance furnace of the Tamman type, a crucible of beryllium oxide with a volume of 171.6 cm ³ with a weighed portion of 150 g of Na ₂ CO ₃ and 50 g of K ₂ CO _{3 was} installed, melted, loaded with 76.7 g of lead and heated to 1000 ^o C , weighed a portion of activated carbon weighing 50 g, which contained 67.1 mg of gold, 4.38 mg of silver. The coal loading was carried out in 4 doses and the melt was held for 1 h for 43 min at a temperature of 100 ^o C, 76.6 g of lead alloy and 61.9 g of molten salts were recovered. The gold content in verkbley was 876 g / t, and silver - 77 g / t. 100% recovery within analysis accuracy. For 1 h, 1.8 g of coal burned per 1 cm ^{2 of the} melt.

Example 2. In the same crucible, 210 g of a mixture of Na ₂ CO ₃ + K ₂ CO _{3 were} charged for 3 hours 25 minutes, activated carbon containing precious metals in an amount of 75.8 g was kept at a temperature of 950 ^o C, 19 g of alloy was recovered lead and 191 g of molten salts. 97.2% of gold and 95% of silver went into metal, the gold content in verkbley was 0.24%.

Example 3. In a crucible with a diameter of 4.2 cm and a height of 9.2 cm, 150 g of Na ₂ CO ₃ were loaded, molten, 34.9 g of lead was charged and for 2 hours 12 minutes at a temperature of 1095 ^° C, the melt loaded onto the surface was oxidized 50 g of catalyst containing 98 mg of gold and 0.122 mg of silver. 39.7 g of lead was poured. The recovery amounted to 96.8% of precious metals. The content of noble metals in verkbley is 25.2%.

 In similar experiments, lead alloys with noble metals containing up to 50% gold and silver were obtained.

 The test results showed that the proposed method provides the complete extraction of precious metals from carbon materials to produce an alloy of any composition depending on the duration of the process (i.e., the accumulation of the noble metal in lead). The process is carried out in one melting unit, is simple, economical and environmentally friendly.

Claims (3)

1. The method of producing precious metals from carbon materials using alkali metal carbonates, characterized in that the starting material in the amount of 2.6 - 6.0% by weight of carbonates is loaded onto the surface of the carbonate melt and kept at 930 - 1100 ^o C until complete oxidation carbon, in this case, before loading the starting material, a metal collector is introduced into the carbonate melt.  2. The method according to p. 1, characterized in that as a melt of carbonates take a mixture of sodium and potassium carbonates in a ratio of 1: 0.3 to 1.  3. The method according to claim 1, characterized in that lead is used as the collector metal.

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